3. Formal: Gradually Don Darker Suits

An all-white suit can be extremely elegant but it's a definite no-go in fall. Similarly, suits in shades like tan or khaki should be worn more and more infrequently as the leaves change color. Instead, start with light gray suits and then begin to gradually make the transition toward dark gray suits (like this one from Tommy Hilfiger) as well as those in more somber shades like navy, dark brown and black. The same rule applies to blazers.